Thermoplastic vulcanisates [TPVs] are general blends of rubber and thermoplastic. These TPVs possess properties that are as good as or maybe better than those of elastomeric block copolymers. TPVs are usually multi-phase polymer systems consisting of hard and soft domains which can either be copolymers or mechanical blends. In these TPVs, the role of elastomer is to improve the impact strength and ductility of the plastic. The stiffness of the elastomer is also increased with the incorporation of plastic into the elastomer matrix.
TPVs comprises of vulcanising rubber which during the melting process mixes well with the molten plastic and is produced by using a dynamic vulcanisation technique. TPVs behave just like conventional elastomeric materials at ambient temperature. However, they can be readily processed just like thermoplastics while being applied with the heat. TPVs possess a good commercial application potential since they do not have to be vulcanised during fabrication into final products. Besides this, TPVs can also be reground and recycled for several times.
Literatures about the use of natural rubber based TPVs for the preparation of conductive materials are very limited to the best of our knowledge. Gomes de Souza Jr. et al [Polymer Testing, Volume 26, 2007] prepared a TPV material which was based on ethylene-vinyl acetate copolymer and nitrile rubber (a type of synthetic rubber), with PAni.DBSA. However, the TPV produced was only semi-electrically conductive with a volume electrical resistivity≥108 ohm-cm and targeted for the application as pressure sensitive devices. Meanwhile, U.S. Patents 2006/0004126 A1, U.S. Pat. No. 7,462,309 B2, 6,624,251 B1 all teach about the preparation of synthetic rubber based TPV materials.
In view of the foregoing, there is a need to provide an improved manufacturing process for manufacturing Hevea Brasiliensis natural rubber based TPV materials which exhibit high electrical conductivities, good tensile properties and high electromagnetic interferences [EMI] shielding effectiveness. Further, it is also a requirement that the manufactured Hevea Brasiliensis natural rubber based TPV materials are highly processable (via injection moulding or extrusion techniques) and also recyclable without significant loss of their good electrical conductivities, tensile properties and EMI shielding effectiveness.
The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.